1. Field of the Invention
The present invention is related to a method for searching a car navigation path by using a log file, more particularly, to a method for searching a navigation path using a log file in a car navigation system, allowing a driver to choose an optimal path out of a path searched by an existing navigation algorithm and a shortest path from the log file the driver himself found out from experiences.
2. Description of the Related Art
In general, a car navigation system using GPS (Global Positioning System) refers to a system for detecting an accurate position of a car, based on data provided by a GPS satellite. Usually more than three GPS satellites are used to provide drivers with real time information about present position and velocity of their cars.
Referring to FIG. 1a, a related art car navigation system using GPS includes a GPS receiver 20 for receiving the position information and velocity data of a car through a GPS receiving antenna 10 from three to four GPS satellites 9; a storage 50 for providing a CD-ROM player with map information obtained from a map database of GIS (Geographic Information System) that stores map data and management data in hierarchical format; micro computer or Micom 30 for searching a map the driver wants to see after calculating a present position of the car in the map coordinate system that is provided by the map database by reading map information provided from the storage 50 and a car position information signal outputted from the GPS receiver 20, and for controlling information about reduction and magnification of the map, and voice output; a display 40 for displaying on a LCD display panel the map, the position information, and additional information provided from the Micom 30; and means for a voice output 60 for receiving an audio signal concerning a search result from the Micom 30 and for outputting a voice for an advance driving path.
Accordingly, when the driver drives his or her car, the car navigation system, more particularly, the Micom 30 therein, provides the driver with car navigation information including the present position and an advance direction of the car, velocity of the car, and road information that are provided by the GPS receiver 20, the car velocity sensor and the storage 50 like a CD-ROM player.
Typically used algorithm for searching the car navigation path is Dijkstra algorithm to find a shortest path from a starting point (a source) to a destination at the earliest possible time. In other words, Dijkstra algorithm is a shortest path algorithm, finding a shortest path among all nodes that are connected to a present source node for a minimum cost.
The shortest path algorithm finds a shortest path for the navigation path searching, by minimum cost precedence. Using a distance from the source, a cost from the source to a final destination is calculated in order to find a node having a minimum cost. The node having a minimum cost becomes a shortest path from the source.
In the shortest path algorithm, variables for calculating the cost are link distance, type of roads (highways, national roads, free ways, local roads), or with or without road.
FIG. 1b is a flow chart showing a guiding procedure for searching a car navigation path according to a related art. As shown in FIG. 1b, a driver selects a destination he wants to go in the car navigation system (S1-S2). Then using weight for each type of roads (e.g., highways, national road, local road or street road in a city), free/toll way, traffic direction, lane weight, or revolution weight (S3), a navigation path is searched out according to Dijakstra or Heuristic shortest path algorithm (S4), and displayed a path to the destination on a navigation map (S7). After map matching following the navigation path (S8), the car navigation system provides path guidance to the driver (S9). When an already registered destination is used in the car navigation system (S5), wherein from a few to tens of destinations that the driver had been are stored in a library for destination (S6), a navigation path to the destination is displayed on the navigation map (S7) to provide a car navigation path to the driver by selecting among stored destinations in case of going to the same destination later (S9).
However, because of manufacture problems of the navigation map, traffic congestion in reality, or difficulties in optimization of the path search algorithm, the car navigation system often fails to search a shortest path to the driver in reality.
As a matter of fact, in many cases, the driver himself reaches the destination via a shorter path than the navigation path search algorithm. Even though communication navigation for providing real time traffic information has been developed, its accuracy is less than 30% and cannot display an actual shortcut on the map of the car navigation system.